Rubber product manufacturers typically receive their raw material in the form of rubber bales that are usually received in large bins. Of course, at one point the bales have to be taken from the bins to feed the fabrication process. Traditionally, those bales are manually removed from the bin, which is physically difficult and time consuming. Some manufacturers use vacuum tools coupled with a gantry type hoist to pick the rubber bales. While this approach is not as physically demanding as the fully manual operation, it still requires manual labor to guide the hoist. Also, the bales located at the bottom of the bin are typically difficult to reach.
Various bin picking technologies are available, but they are designed for small identical parts that are randomly distributed in the bin. Those technologies are not suited to pick rubber bales because, while the bales are orderly placed in the bin, a challenge is to determine their position as the contour of each bale is not obvious to determine, even for the human eye. A sensor system and method typically used for picking of randomly placed objects in a bin would therefore be inappropriate in a rubber bale picking application.
The problems inherent in both identifying and gripping a rubber bale in a bin yield uncertainties in the rubber bale holding condition. This is a drawback considering that a picked bale is to be correctly positioned in an output station.
United States Patent publication no. 2011/0222995 A1, published on Sep. 15, 2011, naming Irie et al. as the inventors and being titled “Robot System and Transfer Method” describes a robot system and method where a shape sensor detects shape information of products randomly placed in a container and an inspection device determines the holding condition of the workpiece by the robot. In the case where the holding condition of the workpiece is found unacceptable, the workpiece is placed on a temporary placement table. The shape sensor is used a second time to detect the workpiece before instructing the robot to retake it.
While the approach taken by Irie et al may be appropriate to pick products that are piled in a bin in an unarranged manner, the proposed shape sensor would be inappropriate to detect edges of the bales considering that there is typically no gap between the rubber bales. This is in addition to Irie's gripping tool that would also be inappropriate for rubber bales. Furthermore, the use of a temporary placement table is detrimental for cycle time reduction purposes.
United States Patent publication no. 2012/0165986 A1, published on Jun. 28, 2012 to Fuhlbrigge et al. and being titles “Robotic picking of parts from a parts holding bin” describes a robot system and method where an image from one or more cameras are used to determine if a robot gripper has picked one or more parts and the position and orientation of the picked part.
The approach taken by Fuhlbrigge et al. is based on the possibility that the gripper can hold more than one part or to return the picked part in the bin if its position and orientation does not meet a predetermined criteria. It is designed for parts that are randomly distributed in a bin and that can therefore be interlocked with each other, which cannot happen for rubber bales. For cycle time purposes, it is preferable to have a system and a method that only picks one part and does not have to return it to the bin regardless of its position and orientation in the gripper.
A system and method that allows bin picking of orderly positioned rubber bales is thus desirable.